The present disclosure relates generally to a level shifter and, in particular, to a level shifter formed with thin-oxide transistors and middle-of-the-line (MOL) capacitors.
Level shifters are used to bring the voltage from a high voltage level (for example 1.8V or more) at a pad of an integrated circuit down to the voltage at the core of the integrated circuit, for example around 0.75V. The high voltage presented at the pad of the integrated circuit may damage the core transistors. In conventional system, the transistors used in the level shifters are formed of thick-oxide transistors and thick-oxide capacitors because the thin-filmed transistors used in the core, which typically break down at a high voltage of 1.2-1.8V, will be damaged by the high voltage presented at the pad.
However, forming the level shifters with more robust thick-oxide transistors has several difficulties, especially when used with newer thin-oxide finFET technologies. Among these difficulties, thick-oxide structures are large and bulky and therefore the use of such structures inherit a severe area penalty for producing thick oxide structures close to thin oxide structures. Additionally, the need for at least three extra masks (oxide and source/drain implants) to form the thick oxides results in additional costs of manufacture.
Accordingly, it would be desirable to provide better level shifters that accommodate the shift from a high input voltage to a lower voltage appropriate for use with thin-oxide structures.